1. Field of the Invention
This invention relates to a recording apparatus such as, for example, a digital audio tape recorder or a data storage device for performing reliable data recording.
2. Description of the Related Art
There has hitherto been know a data storage device for recording data supplied from an information processing apparatus, such as a personal computer or a workstation, on a magnetic tape. With such a data storage device, a rotary head is used for recording data on a recording track inclined relative to the tape's running direction for improving the data recording density. There has also been known a digital audio tape recorder (DAT) in which, a rotary head is used for recording/reproducing speech as digital data on a recording track inclined relative to the tape's running direction.
With the data storage device or DAT, so-called product codes (parity data) are appended as error correction codes when recording data in order to improve data reliability.
With such DAT, 196 blocks of data are recorded in each track, as shown for example in FIG. 1A. In such a recording track, 11 blocks of margin areas are provided on both ends thereof and, between these margin areas, there are provided eight blocks each of first and second sub-code areas for recording sub-codes, five blocks each of two ATF areas for recording automatic track finding (ATF) signals for effecting tracking control and 128 blocks of a main data area for recording data.
The sub-code area and the main data area are each made up of blocks made up of 288 bits. Each block defining the main data area is made up of an 8-bit synchronization signal, main IDs (W1 and W2) each composed of 8 bits, 8-bit parity data and 356-bit PCM data, as shown in FIG. 1B. In each of the main IDs (W1 and W2), there are recorded a PCM (pulse code modulation)-ID for specifying the quantization methods for speech signals and block addresses for identifying respective blocks.
Each block defining the subcode area is made up of an 8-bit synchronization signal, sub-IDS (W1, W2) each made up of 8-bits, a parity code of 8 bits, and subcode data of 256 bits, as shown in FIG. 1C. In the sub-IDs (W1, W2) are recorded the sub-code ID specifying the types of the sub-code, block addresses for specifying the blocks, and the sub-code ID.
The main data, temporally continuously supplied from an external audio apparatus or the like so as to be recorded in each block of the main data area, is interleaved, that is, re-arrayed, before appendage of error correction codes.
By performing the interleaving before recording, if data failure is produced in succession in data of respective blocks due to dropout in the magnetic tape during reproduction, data dropout may be temporally distributed in the ultimately reproduced speech data.
With the above DAT, it is possible to perform a so-called read-after-write operation of sequentially reproducing a recorded track for comparison with recorded data. When performing such a read-after-write operation, the number of times error correction is performed on the reproduced data using the parity data recorded as described above, referred to hereinafter, as the number of syndrome occurrences, is detected, and the number of syndrome occurrences is compared to a pre-set threshold value. If the number of syndrome occurrences exceeds the pre-set threshold value, the same data is again recorded. This enables data to be correctly recorded on the magnetic tape.
However, when performing such a read-after write operation, there are occasions wherein recording becomes infeasible due to head clogging, in which magnetic particles become affixed to the head gap of the magnetic head which renders recording impossible. If, in such case, a previously recorded recording track is left on the magnetic tape, the reproducing head reproduces the previously recorded recording track. The result is that, if the number of syndrome occurrence is less than the above threshold value, it may be judged through error that correct recording has been made, even although no recording has actually been made.
It may be contemplated to reproduce the data recorded on a magnetic tape and to correct errors in all the reproduced data in order to corroborate whether all the data has been corrected for errors. Since error correction needs to be performed on all the data, corroboration of the recorded data becomes extremely time-consuming.
It may also be contemplated to store all the data recorded on a magnetic tape and to compare the stored data to the reproduced data. In this case, a large storage unit is required for storing the recorded data, so that comparison of all the data becomes similarly time-consuming.
It may likewise be contemplated to correct only part of the recorded data for effecting high-speed recording in order to corroborate whether recording has been made correctly. In this case, it is impossible to detect errors produced in areas other than those where error correction has been performed, thus lowering reliability.